Generally, when a reinforced concrete beam or pillar is crushed or when an oblique reinforced concrete member is crushed with a crusher, it is preferred to apply a shearing force to the concrete member or the like perpendicular to its axis. A known rotatable crusher of this type is disclosed, for example, in Japanese Patent Application laid-open No. 60-62373. Therein, even if the hydraulic excavator is maintained unmoved, an object to be crushed can be broken by a crusher because the angle of the crusher to the object is changeable so that the crusher can be positioned perpendicular to the longitudinal axis of the object, if necessary.
To crush an object such as a reinforced concrete beam or pillar, an excessive load of many tons is applied as a bending moment to the rotational mechanism of the crusher even if the crusher is positioned rotatable to an appropriate position. Therefore, tends to occur early in that rotational mechanism. Thus, the crushing capability is lowered, making it very difficult to crush the object, which is a serious drawback with the prior art.
In order to eliminate such play, it is necessary to repair the whole crusher or to replace the defective crusher with a new one, which would interrupt work as well as be dangerous.
If the crusher is reversed to an appropriate position in a narrow space, a structure or an object, such as an adjacent wall, which should not be crushed could be destroyed, which is also a serious problem.